Air compressor

ABSTRACT

An air compressor includes a motor provided with a basic insulation, a first air compressing unit and a second air compressing unit that are driven by the motor, at least two tanks, and a discharge port. The at least two tanks are connected to the first air compressing unit and the second air compressing unit, store air compressed by the first air compressing unit and the second air compressing unit, and are connected to one another in series. The discharge port is disposed to a tank positioned on a most downstream of supplied compressed air and discharges the compressed air. The motor, the first air compressing unit and the second air compressing unit, and a tank on an upstream side with respect to the tank positioned on the most downstream are electrically insulated from the tank positioned on the most downstream and the discharge port.

This application claims the benefit of International Application No. PCT/JP2020/040501 filed on Oct. 28, 2020 and Japanese Patent Application Number 2019-199075 filed on Oct. 31, 2019, the entirety of which is incorporated by reference.

BACKGROUND OF THE INVENTION Technical Field

The present invention relates to an air compressor in which an air compressing unit is driven by a motor to store compressed air in a tank.

Background Art

In an air compressor, an electric power tool, and the like, basic insulation is provided to a charging unit, such as a motor, a controller, and other electronic parts.

For example, in a brushcutter disclosed in JP-A-2016-93132, an insulators is interposed between respective teeth of a stator core of a brushless motor and coils to perform the basic insulation.

SUMMARY OF THE INVENTION

However, in an air compressor, since a metallic housing that houses a motor and an air compressing unit and a metallic tank are exposed, it is preferred to enhance insulation performance.

Therefore, an object of the present invention is to provide an air compressor in which insulation performance is enhanced.

In order to achieve the above-described object, in one aspect of the present invention, an air compressor includes a motor provided with a basic insulation, a first air compressing unit and a second air compressing unit, at least two tanks, and a discharge port. The first air compressing unit and the second air compressing unit are driven by the motor. The at least two tanks are connected to the first air compressing unit and the second air compressing unit, store air compressed by the first air compressing unit and the second air compressing unit, and are connected to one another in series. The discharge port is disposed to a tank positioned on a most downstream of supplied compressed air and discharges the compressed air. The motor, the first air compressing unit and the second air compressing unit, and a tank on an upstream side with respect to the tank positioned on the most downstream are electrically insulated from the tank positioned on the most downstream and the discharge port.

In order to achieve the above-described object, in another aspect of the present invention, an air compressor includes a motor provided with a basic insulation, a first air compressing unit and a second air compressing unit, at least two tanks, and a discharge port. The first air compressing unit and the second air compressing unit are driven by the motor. The at least two tanks are connected to the first air compressing unit and the second air compressing unit, store air compressed by the first air compressing unit and the second air compressing unit, and are connected to one another in series. The discharge port is disposed to a tank positioned on a most downstream of supplied compressed air and discharges the compressed air. The motor, the first air compressing unit and the second air compressing unit, and all the tanks are electrically insulated from the discharge port.

In another aspect of the present invention, which is in the above configuration, the electrical insulation may be performed by interposing a resin-made tubular body in a connecting pipe connecting the tank on the upstream side to the tank positioned on the most downstream, and by supporting the first air compressing unit and the second air compressing unit on the tank positioned on the most downstream via a resin member.

In another aspect of the present invention, which is in the above configuration, an insulating bush may be further interposed between the tank positioned on the most downstream and the discharge port.

In another aspect of the present invention, which is in the above configuration, the electrical insulation may be performed by interposing an insulating bush between the tank positioned on the most downstream and the discharge port.

In another aspect of the present invention, which is in the above configuration, at least the motor, the first air compressing unit and the second air compressing unit, and the tank on the upstream side may be covered with a resin-made outer housing.

In another aspect of the present invention, which is in the above configuration, the motor, the first air compressing unit and the second air compressing unit, and all the tanks may be covered with a resin-made outer housing.

In another aspect of the present invention, which is in the above configuration, the outer housing may include a lower housing and an upper housing. The tanks are placed on the lower housing. The upper housing is assembled to the lower housing from above the lower housing.

In another aspect of the present invention, which is in the above configuration, the lower housing and the upper housing may be assembled with a screw, and an exposed portion of the screw in the outer housing may be covered with a resin-made cover.

In another aspect of the present invention, which is in the above configuration, assembling of the lower housing and the upper housing may be performed by screwing each of the screw passing through the lower housing and the screw passing through the upper housing into a metal fitting positioned in the outer housing.

In another aspect of the present invention, which is in the above configuration, the metal fitting may be also covered with the cover.

In another aspect of the present invention, which is in the above configuration, positioning of the metal fitting may be performed by inserting the metal fitting into a framing portion disposed in the lower housing and having an opened upper surface.

In another aspect of the present invention, which is in the above configuration, the lower housing may include a bottom plate and a side plate formed to rise around an outer periphery of the bottom plate, and the framing portion is formed on an inner side of the side plate.

In another aspect of the present invention, which is in the above configuration, the metal fitting may include a lower plate formed along a bottom surface in the framing portion and a vertical plate formed along the side plate such that the metal fitting has an L-shape, and the screw passing through the lower housing and the screw passing through the upper housing may be screwed into the lower plate and the vertical plate, respectively.

In another aspect of the present invention, which is in the above configuration, the cover may be fitted to the framing portion from above the metal fitting.

In another aspect of the present invention, which is in the above configuration, assembling of the lower housing and the upper housing with the screws may be performed at a plurality of positions.

In another aspect of the present invention, which is in the above configuration, the upper housing may be formed by assembling a plurality of divided housings.

In another aspect of the present invention, which is in the above configuration, the discharge port may be exposed to an outside via a through hole provided in the outer housing.

In another aspect of the present invention, which is in the above configuration, a carry handlebar may be disposed in the outer housing.

In another aspect of the present invention, which is in the above configuration, a pressure reducing valve and an operating member with which a pressure of the pressure reducing valve is adjustable may be disposed between a second tank and the discharge port, and the operating member may be exposed to an outside via a through hole provided in the outer housing.

In another aspect of the present invention, which is in the above configuration, the tank positioned on the most downstream may be exposed.

The present invention provides a double insulation structure in which at least the discharge port is electrically insulated from an internal metal, in addition to the basic insulation. Accordingly, the insulation performance can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view from the right side of an air compressor.

FIG. 2 is an exploded perspective view of an outer housing.

FIG. 3 is a front view of the air compressor from which an upper housing is omitted.

FIG. 4 is a right side view of the air compressor from which the upper housing is omitted.

FIG. 5 is a cross-sectional view taken along a line A-A in FIG. 3.

FIG. 6 is a cross-sectional view taken along a line B-B in FIG. 3.

FIG. 7 is a cross-sectional view taken along a line C-C in FIG. 3.

FIG. 8 is a vertical cross-sectional view illustrating an insulation structure of a take-out pipe.

FIG. 9 is a vertical cross-sectional view illustrating an insulation structure of a connecting pipe.

FIG. 10 is an exploded perspective view illustrating an insulation structure of the connecting pipe.

FIG. 11 is an enlarged cross-sectional view of a mating portion of the upper housing.

FIG. 12 is an enlarged cross-sectional view of a screwing portion of a lower housing and the upper housing.

FIG. 13 is a perspective view of the air compressor from which the front side of the upper housing is removed.

FIG. 14 is a vertical cross-sectional view illustrating a modification example of an insulation structure of the take-out pipe.

FIG. 15 is a perspective view an air compressor illustrating a modification example of the take-out pipe.

DETAILED DESCRIPTION OF THE INVENTION

The following describes embodiments of the present invention based on the drawings.

FIG. 1 is a perspective view illustrating an example of an air compressor. FIG. 2 is an exploded perspective view of an outer housing. FIG. 3 and FIG. 4 are a front view and a right side view of the air compressor from which an upper housing is omitted.

In the description of an air compressor 1, a tank 2B side is defined as front, a tank 2A side is defined as rear, and the longitudinal direction of the tanks 2A, 2B is defined as right-left direction.

The air compressor 1 includes a pair of tanks 2A, 2B, a base 3, a main unit 4, and an outer housing 5. The tanks 2A, 2B and an inner housing 6 of the main unit 4 are made of metal. The base 3 and the outer housing 5 are made of resin.

The tanks 2A, 2B extend in the right-left direction and are supported in parallel and horizontally with one another. The tanks 2A, 2B are connected in series by a connecting pipe 7 and have the same internal pressure. The base 3 is secured across the tanks 2A, 2B above the tanks 2A, 2B. The main unit 4 is secured on the base 3.

The main unit 4 has a motor 10 and two air compressing units 11A, 11B inside the tubular inner housing 6. The inner housing 6 is supported on the base 3 in a posture that an axis line of the inner housing 6 becomes the front-rear direction. The air compressing units 11A, 11B each project from the inner housing 6 in the right-left direction. A pipe 12 is connected between the air compressing unit 11A and the air compressing unit 11B, and a pipe 13 is connected between the air compressing unit 11B and the tank 2A.

As illustrated in FIG. 5 and FIG. 6, the motor 10 includes a stator 15 and a rotor 16. The stator 15 is secured to a tubular portion 8 formed on the front side of the inner housing 6. The rotor 16 is arranged on an outer side of the stator 15 and rotatably supported to the inner housing 6. The motor 10 is an outer rotor type brushless motor.

The stator 15 includes a stator core 17, a plurality of insulators 18, 18 . . . , and a plurality of coils 19, 19. . . . The stator core 17 and the coils 19 are insulated (basically insulated) by the insulators 18.

The stator core 17 is formed of a magnetic material. The stator core 17 includes a ring-shaped base portion 20 and a plurality of teeth 21, 21 . . . disposed to protrude radially from the base portion 20.

The respective insulators 18 are formed of a resin material and secured in a state of coating the respective teeth 21. The respective insulators 18 are each integrally linked to a resin-made covering portion 22 covering the front and rear surfaces of the base portion 20. In the covering portion 22, an outer ring 23 and an inner ring 24 are concentrically formed on the inner side of the respective coils 19. The outer ring 23 is formed longer in the front and rear than the coil 19.

On the rear side of the stator core 17, an arc-shaped sensor circuit board 25 is disposed. The sensor circuit board 25 is supported via the insulators 18 and the outer ring 23. The sensor circuit board 25 includes a rotation detecting element (not illustrated) detecting a magnetic field of a magnet 38 disposed in the rotor 16, which is described later.

The respective coils 19 are formed such that a wire is wound around the four teeth 21, 21 . . . via the insulators 18 so as to form each of a U-phase, a V-phase, and a W-phase. The coils 19 are connected to a controller 90 described later via three-phase power lines.

The rotor 16 has a rotation shaft 30, a rotor core 31, and a coupling tube 33. The rotation shaft 30 is formed of a magnetic material and supported in the inner center of the inner housing 6 via bearings 32, 32. The rotor core 31 has a cup shape having a large diameter and is coupled to the front end of the rotation shaft 30.

The rotation shaft 30 has both front and rear ends projecting from the inner housing 6. The coupling tube 33 is coaxially and integrally coupled to the front end of the rotation shaft 30 by a bolt. The coupling tube 33 has an outer periphery to which a flange 34 is circularly disposed. A fan 35 is integrally secured to the front end of the coupling tube 33 that passes through the rotor core 31. A fan 36 is also integrally secured to the rear end of the rotation shaft 30 that projects from the inner housing 6.

The rotor core 31 is coupled to the flange 34 of the coupling tube 33 from the front by a bolt. The rotor core 31 has a peripheral wall portion 37 that overlaps an outer side of the stator core 17 in a radial direction. The cylindrical magnet 38 is arranged on the inner periphery of the peripheral wall portion 37 positioned on outer sides of the respective teeth 21. The magnet 38 is magnetized so that an N-pole and an S-pole alternately appear.

In the inner housing 6, a pair of front and rear cams 40, 40 are integrally secured to the rotation shaft 30. The cams 40, 40 are made eccentric with a phase of 180° shifted around the axis of the rotation shaft 30. A cam ring 42 is externally mounted to each of the cams 40 via a bearing 41.

The air compressing units 11A, 11B includes cylinders 43, 43 projecting to the right and left from the inner housing 6. Each of the cylinders 43 houses a piston 44. The cam ring 42 is coupled to the piston 44 via a connecting rod 45. In each of the cylinders 43, a cylinder chamber 46 that houses the piston 44 is formed.

When the rotation shaft 30 rotates, the respective cams 40 eccentrically move. Accordingly, via the connecting rod 45, the rotational motion of the rotation shaft 30 is converted into reciprocation motion of the pistons 44, 44 in the cylinders 43, 43. The pistons 44, 44 reciprocate at timings such that the pistons 44, 44 are opposite to one another by the cams 40, 40. Thus, the air compressing units 11A, 11B alternately compress air in the cylinder chambers 46, 46 by the reciprocation of the pistons 44, 44 to supply the compressed air to the tanks 2A, 2B. Specifically, first, an external pressure is compressed in the cylinder chamber 46 on the air compressing unit 11A side. The compressed air is sent to the cylinder chamber 46 on the air compressing unit 11B side via the pipe 12 and further compressed. The compressed air is sent to the tank 2A via the pipe 13 and sent to the tank 2B via the connecting pipe 7.

As illustrated in FIG. 3, FIG. 6, and FIG. 7, metallic mounting portions 50A, 50A and metallic mounting portions 50B, 50B are secured in the right and left respectively on the upper surfaces of the tanks 2A, 2B. The base 3 includes a pair of right and left installation portions 51, 51. The installation portions 51, 51 extend in the front-rear direction across the front and rear mounting portions 50A, 50B positioned on the right and left of the tanks 2A, 2B. The base 3 also includes a coupling portion 52 in the right-left direction that links the right and left installation portions 51, 51 between the tanks 2A, 2B. The coupling portion 52 has a box shape opening downward. The installation portions 51, 51 have both front and rear ends secured to the mounting portions 50A, 50B of the tanks 2A, 2B by respective screws 51 a, 51 a. Thus, the base 3 is secured on the tanks 2A, 2B.

On the lower side of the inner housing 6, two pairs of leg portions 53, 53 projecting to both right and left sides are disposed to protrude such that each pair of the leg portions 53, 53 is provided in the front and rear. The right and left leg portions 53, 53 are secured to the installation portions 51, 51 of the base 3 via coupling metal fittings 54, 54 by respective screws 54 a, 54 a. Thus, the main unit 4 is secured on the base 3. The coupling metal fittings 54, 54 and the screws 54 a, 54 a in the installation portion 51 are located between the mounting portions 50A and 50B and also between the screws 51 a and 51 a. Accordingly, metal materials are not in contact with one another between the leg portions 53, 53 and the mounting portions 50A, 50B.

On the right side of the main unit 4, take-out pipes 60A, 60B for air pressure are connected to the tanks 2A, 2B. FIG. 8 illustrates a vertical cross section of the take-out pipe 60A part. The take-out pipe 60B has the same structure. Pressure reducing valves 61A, 61B are respectively disposed in the take-out pipes 60A, 60B. The pressure reducing valves 61A, 61B have upper ends at which adjusting knobs 62A, 62B are disposed, respectively. Rotating operation of the adjusting knobs 62A, 62B allows for adjusting an air pressure that can be taken out within a predetermined range. Here, the take-out pipe 60B on the front side is for high pressure, and the take-out pipe 60A on the rear side is for general pressure.

On the downstream side (secondary side) of the pressure reducing valves 61A, 61B, coupler manifolds 63A, 63B are mounted to the take-out pipes 60A, 60B. A pair of joints 64A, 64A and a pair of joints 64B, 64B for air hose connection are disposed to the coupler manifolds 63A, 63B, respectively. The pair of joints 64A, 64A and the pair of joints 64B, 64B are arranged one above the other.

Tubular resin bushes 65A, 65B are interposed between the take-out pipes 60A, 60B and the tanks 2A, 2B. Here, for connection, the lower ends of the resin bushes 65A, 65B are screwed into connection ports 66A, 66B of the tanks 2A, 2B, and the lower ends of the take-out pipes 60A, 60B are screwed into the upper ends of the resin bushes 65A, 65B. The metallic tanks 2A, 2B and the metallic joints 64A, 64B are electrically insulated by the resin bushes 65A, 65B.

A pressure sensor 70 is disposed on the right side on the tank 2B. The pressure sensor 70 is connected to the coupler manifolds 63A, 63B of the take-out pipes 60A, 60B via tubes 71, 71 to detect the air pressure on the secondary side of the pressure reducing valves 61A, 61B. The detected air pressure is output to the controller 90. The tubes 71, 71 are formed of an insulating material, such as fluorine resin. Accordingly, even when the pressure sensor 70 is connected to the take-out pipes 60A, 60B, the electrical insulation of the joints 64A, 64B is ensured.

The electrical insulation is provided also to the connecting pipe 7 that links the tanks 2A, 2B to one another.

As illustrated in FIG. 9 and FIG. 10, a metallic inner cylinder 75 is connected to the upper surface of the tank 2B to which the connecting pipe 7 is connected. The inner cylinder 75 includes an internal flow passage 76 in the axial center. The internal flow passage 76 has a lower end communicated with the inside of the tank 2B and an upper end being closed. The internal flow passage 76 has an upper end at which a through hole 77 communicated with an outside is formed in a radial direction. The inner cylinder 75 has an intermediate portion in which a receiving portion 78 having a large diameter is formed. A small diameter portion 79 is formed on the outer periphery of the inner cylinder 75 above the receiving portion 78. The through hole 77 opens to the small diameter portion 79.

An intermediate cylinder 80 is externally mounted to the outer periphery of the inner cylinder 75. The intermediate cylinder 80 is divided into two parts of an upper cylinder 80 a and a lower cylinder 80 b, which are both made of resin. The upper cylinder 80 a and the lower cylinder 80 b have overlapping portions 81, 81 that are contactlessly overlapped in the radial direction at an outer side of the small diameter portion 79. A communication passage 82 is formed between the overlapping portions 81, 81 so as to communicate the outer side of the small diameter portion 79 with an outer side of the intermediate cylinder 80. The inner cylinder 75 has an upper end to which a circular plate 83 retaining the intermediate cylinder 80 is secured.

A metallic outer cylinder 84 is externally mounted to the outer side of the intermediate cylinder 80. The outer cylinder 84 has an inlet 85 that communicates with the communication passage 82 and protrudes in the radial direction. The inlet 85 is connected to the connecting pipe 7.

Accordingly, the outer cylinder 84 to which the connecting pipe 7 connected to the tank 2A is connected is electrically insulated from the inner cylinder 75 connected to the tank 2B by the intermediate cylinder 80. The compressed air from the connecting pipe 7 passes through the communication passage 82 of the intermediate cylinder 80 from the inlet 85 of the outer cylinder 84, reaches the internal flow passage 76 from the through hole 77, and flows to the tank 2B.

The controller 90 is disposed between the tanks 2A, 2B. As illustrated in FIG. 5 and FIG. 7, the controller 90 is supported in a vertical posture extending in the right-left direction by an installation plate 91 in the right-left direction that is secured to the inner side of the coupling portion 52 of the base 3. The controller 90 is electrically connected to the pressure sensor 70 to become an internal metal together with the tank 2A. However, since the base 3 is interposed between the controller 90 and the tank 2B, the tank 2B is electrically insulated also from the controller 90.

The controller 90 holds a control circuit board 92 forming an inverter circuit or the like. The control circuit board 92 drives the motor 10 in association with an operation of an operation panel (not illustrated) disposed on an outer surface of the outer housing 5. The rotation speed of the motor 10 is controlled by selecting an operation mode on the operation panel and the operation state is displayed on the operation panel.

As illustrated in FIG. 1 and FIG. 2, the outer housing 5 has a lower housing 100 and an upper housing 101. The lower housing 100 is arranged on the lower side of the tanks 2A, 2B to cover from below the tanks 2A, 2B. The upper housing 101 is assembled on the upper side of the lower housing 100 to cover the tanks 2A, 2B and the main unit 4 from thereabove.

The lower housing 100 has a bottom plate 102 and a side plate 103. The bottom plate 102 has a rectangular shape in a plan view in which the tanks 2A, 2B are fit. The side plate 103 is formed upward around the outer periphery of the bottom plate 102 over the whole circumference. The side plate 103 has an upper side part that constitutes an expanded opening portion 104 expanding to the outer side over the whole circumference. Legs 105, 105 . . . having a circular shape in a plan view are mounted to four corners on the lower surface of the bottom plate 102.

The upper housing 101 includes a plurality of through holes 106, 106 . . . that expose the adjusting knobs 62A, 62B of the take-out pipes 60A, 60B and the respective joints 64A, 64B. A pair of handlebars 107, 107 extending in the front and rear are disposed in the upper right and left of the upper housing 101.

The upper housing 101 is divided into front and rear parts with the center in the front-rear direction as a border. Divided halved housings 101 a, 101 b are coupled with one another by a plurality of screws 108, 108 . . . in the right-left direction. Specifically, as illustrated in FIG. 11, for coupling, on the inner sides of both mating surfaces, the screws 108 that pass through a plurality of tubular bosses 109, 109 . . . disposed in the halved housing 101 b are screwed into a plurality of screw bosses 110, 110 . . . disposed in the halved housing 101 a. A packing (not illustrated), such as an O-ring, is interposed between the mating surfaces of the halved housings 101 a, 101 b over the overall length for a countermeasure against rain water.

The upper housing 101 has a lower portion assembled so as to surround the outer side of the side plate 103 of the lower housing 100. As illustrated in FIG. 12, on the lower portion of the upper housing 101, a lower lock portion 111 that locks the lower end of the expanded opening portion 104 of the side plate 103 from therebelow and an upper lock portion 112 that locks the upper end of the expanded opening portion 104 from thereabove are formed over the whole circumference.

In a state where the expanded opening portion 104 is locked between the lower lock portion 111 and the upper lock portion 112, the upper housing 101 and the expanded opening portion 104 are coupled with one another by a plurality of screws 113, 113 . . . screwed from the outer sides of the respective front, rear, right, and left surfaces.

As illustrated in FIG. 12, coupling by the screws 113 is performed using a plurality of framing portions 114 and metal fittings 115. The framing portions 114 have a square shape in a plan view and are formed on the inner side of the expanded opening portion 104, and metal fittings 115 are arranged in the respective framing portions 114.

The respective framing portions 114 are formed on the upper surfaces of a plurality of bottom raising portions 116, 116 . . . formed on the upper surface of the bottom plate 102.

The metal fitting 115 has an L-shape in a side view that has a lower plate 117 positioned on the upper side of the bottom raising portion 116 and a vertical plate 118 positioned on the inner side of the expanded opening portion 104. Respective screw-holes 119, 119 are formed orthogonally in the lower plate 117 and the vertical plate 118. The metal fitting 115 is inserted into the framing portion 114 from thereabove and positioned in the framing portion 114 on the bottom raising portion 116.

Here, from below the bottom plate 102, a screw 121 that passes through the bottom raising portion 116 via a washer 120 is screwed into the screw-hole 119 of the lower plate 117 of the metal fitting 115. Then, the metal fitting 115 is secured inside the framing portion 114.

Next, from the outer side of the upper housing 101, the screw 113 that passes through the upper housing 101 via the washer 120 is screwed into the screw-hole 119 of the vertical plate 118 of the metal fitting 115. Then, the upper housing 101 is secured to the side plate 103. At this time, the upper lock portion 112 projects to the inner side of the upper housing 101 over the expanded opening portion 104 and covers from above the vertical plate 118.

A cover 122 is disposed in each of the framing portions 114. The cover 122 is made of resin formed in an arc shape in a side view between the distal end of the lower plate 117 of the metal fitting 115 and the upper end of the vertical plate 118. On both sides of the cover 122, bent pieces 123, 123 folded below along the inner surface of the framing portion 114 are integrally formed.

The cover 122 has one end that abuts on the upper end of the vertical plate 118 below the upper lock portion 112 and the other end that abuts on the distal end of the lower plate 117 on the inner side of the framing portion 114 when fitted to the framing portion 114 from above the metal fitting 115. In this state, the metal fitting 115 and the screws 113, 121 are covered with the cover 122 and are not exposed to the inside of the outer housing 5.

In the air compressor 1 configured as described above, in a state where the metal fittings 115 and the covers 122 are mounted to the lower housing 100, the tanks 2A, 2B and the main unit 4 are placed on the bottom plate 102. Next, covered with the upper housing 101, the lower portion of the upper housing 101 is locked to the expanded opening portion 104 of the side plate 103 for positioning. Subsequently, the screws 113 are screwed into the metal fittings 115 from the outer side of the upper housing 101. Then, as described above, the air compressor 1 is covered in whole with the outer housing 5 excluding the adjusting knobs 62A, 62B and the respective joints 64A, 64B that are exposed via through holes 106. As described above, the adjusting knobs 62A, 62B and the respective joints 64A, 64B are electrically insulated from the internal metals, such as the tank 2A and the inner housing 6 by the resin bushes 65A, 65B, so that the adjusting knobs 62A, 62B and the respective joints 64A, 64B become external metals.

When the air compressor 1 is used, a power supply button is pressed after the operation mode is selected with a mode switch button disposed on the operation panel. Then, power is supplied to the respective coils 19 of the stator 15 of the motor 10, and the rotor 16 rotates. Specifically, the control circuit board 92 of the controller 90 obtains a rotation detection signal that indicates the position of the magnet 38 of the rotor 16, which is output from the rotation detecting element of the sensor circuit board 25, and acquires a rotation state of the rotor 16. Depending on the acquired rotation state, the control circuit board 92 controls ON/OFF of a mounted FET and rotates the rotor 16 by energizing the three-phase coils 19 in turn.

When the rotor 16 rotates, the rotation shaft 30 also integrally rotates. Then, as described above, the air compressing units 11A, 11B are driven and the compressed air compressed in two stages is supplied to the tanks 2A, 2B. The compressed air stored in the tanks 2A, 2B can be taken out via air hoses connected to the respective joints 64A, 64B.

The fans 35, 36 in the front and rear of the rotation shaft 30 rotate, suction external air from an air inlet (not illustrated) disposed in the outer housing 5, and let the external air pass inside the outer housing 5. Accordingly, the main unit 4 including the motor 10 and the air compressing units 11A, 11B can be cooled.

In the motor 10, the insulation (basic insulation) between the stator core 17 and the coils 19 is ensured by the insulators 18. In addition to this, the electrical insulation by the base 3, the electrical insulation by the resin bushes 65A, 65B and the tubes 71, 71, and the electrical insulation by the intermediate cylinder 80 at the connecting pipe 7 are provided. Thus, the tank 2B and the respective joints 64A, 64B are electrically insulated from the main unit 4, tank 2A, and the controller 90, which become the internal metals, and the tank 2B and the respective joints 64A, 64B become the external metals. Accordingly, the insulation performance of the air compressor 1 can be enhanced.

In addition to being covered in whole with the outer housing 5, the screws 113, 121 that assemble the outer housing 5 are also covered with the cover 122. Accordingly, the main unit 4 and tank 2A and the controller 90 are also electrically insulated from the outside. The screws 113, 121 of the outer housing 5, the adjusting knobs 62A, 62B, and the respective joints 64A, 64B are also electrically insulated from the outside.

Thus, the tank 2B and the respective joints 64A, 64B become the external metals, thereby allowing for exposing the tank 2B side by removing the front side of the upper housing 101 as illustrated in FIG. 13. Exposing in this way can obtain heat radiation effect. Naturally, the shape of the upper housing 101 is not limited to this, and the upper housing may be formed so as to cover the whole of the internal metals, such as the main unit 4 including the tank 2A and the connecting pipe 7. Further, as illustrated in FIG. 3 and FIG. 4, the whole upper housing 101 can be removed.

The air compressor 1 of the above-described configuration includes the motor 10 provided with the basic insulation by the insulators 18, and the air compressing unit 11A (first air compressing unit) and the air compressing unit 11B (second air compressing unit) that are driven by the motor 10. The air compressor 1 also includes the tanks 2A, 2B that are connected to the air compressing units 11A, 11B, store the air compressed by the air compressing units 11A, 11B, and are connected to one another in series. The air compressor 1 includes the joints 64B, 64B (discharge ports) for discharging the compressed air which are disposed to the tank 2B (tank positioned on the most downstream of the compressed air). In the air compressor 1, the motor 10, the air compressing units 11A, 11B, and the tank 2A (tank on the upstream side with respect to the tank positioned on the most downstream) are electrically insulated from the tank 2B and the joints 64B, 64B by the base 3 and the intermediate cylinder 80.

With the configuration, the air compressor 1 has a double insulation structure in which the tank 2B and the joints 64B, 64B are also electrically insulated from the internal metals, in addition to the basic insulation by the insulators 18. Accordingly, the insulation performance can be enhanced.

In particular, the electrical insulation is performed by interposing the resin-made intermediate cylinder 80 (tubular body) in the connecting pipe 7 connecting the tanks 2A, 2B and by supporting the air compressing units 11A, 11B via the base 3 (resin member) on the tanks 2A, 2B. Accordingly, the tank 2B and the joints 64B, 64B can be easily electrically insulated.

The resin bush 65B (insulating bush) is further interposed between the tank 2B and the joints 64B, 64B. Accordingly, the joints 64B, 64B can be surely electrically insulated from the internal metals.

The motor 10, the air compressing units 11A, 11B, and the tank 2A are covered with the resin-made outer housing 5. Accordingly, the motor 10, the air compressing units 11A, 11B, and the tank 2A that become the internal metals can be electrically insulated from the outside.

The resin bush 65A is interposed between the tank 2A and the take-out pipe 60A. Accordingly, even when the take-out pipe 60A is provided to the tank 2A that becomes the internal metal, the joints 64A, 64A can be electrically insulated.

As another invention, the air compressor 1 includes the motor 10 provided with the basic insulation by the insulators 18, and the air compressing unit 11A (first air compressing unit) and the air compressing unit 11B (second air compressing unit) that are driven by the motor 10. The air compressor 1 also includes the tanks 2A, 2B that are connected to the air compressing units 11A, 11B, store the air compressed by the air compressing units 11A, 11B, and are connected to one another in series. The air compressor 1 includes the joints 64B, 64B (discharge ports) for discharging the compressed air which are disposed to the tank 2B (tank positioned on the most downstream of the compressed air). In the air compressor 1, the motor 10, the air compressing units 11A, 11B, and the tanks 2A, 2B are electrically insulated from the joints 64B, 64B by the resin bush 65B.

With the configuration, the air compressor 1 has a double insulation structure in which the joints 64B, 64B are also electrically insulated, in addition to the basic insulation by the insulators 18. Accordingly, the insulation performance can be enhanced.

The outer housing 5 includes the lower housing 100 on which the tanks 2A, 2B are placed and the upper housing 101 assembled to the lower housing 100 from thereabove. Accordingly, the whole tanks 2A, 2B can be completely covered.

The lower housing 100 and the upper housing 101 are assembled with the screws 113, 121, and exposed portions of the screws 113, 121 in the outer housing 5 are covered with the resin-made cover 122. Accordingly, the screws 113, 121 with which the divided lower housing 100 and the upper housing 101 are assembled are not exposed to the internal metals, such as the tank 2A.

Assembling of the lower housing 100 and the upper housing 101 is performed by screwing each of the screws 121 passing through the lower housing 100 and the screws 113 passing through the upper housing 101 into the metal fittings 115 positioned in the outer housing 5. Accordingly, assembling of the lower housing 100 and the upper housing 101 can be easily performed using the metal fittings 115.

Since the metal fittings 115 are also covered with the cover 122, the metal fittings 115 are not exposed to the internal metals, such as the tank 2A, even when used.

The insulation structure in the take-out pipe is not limited to the above-described configuration.

For example, as illustrated in FIG. 14, the respective resin bushes 65A, 65A (65B, 65B) may be interposed between the coupler manifold 63A (63B) of the take-out pipe 60A (60B) and the joints 64A, 64A (64B, 64B). Here, one end of the resin bush 65A (65B) is screwed into the coupler manifold 63A (63B), and the joint 64A (64B) is screwed into the other end of the resin bush 65A (65B).

On the other hand, as another modification example, as illustrated in FIG. 15, a branch pipe 67 may be connected in the front-rear direction to the take-out pipe 60B of the tank 2B, and the take-out pipe 60A may be connected to the rear end of the branch pipe 67. Accordingly, the take-out pipes 60A, 60B are both connected to the tank 2B that becomes the external metal.

In FIG. 15, when it is not necessary for the adjusting knobs to separate in the front and rear, the branch pipe 67 may be shortened and the take-out pipes 60A, 60B may be arranged on the tank 2B side. The resin bush 65B may be interposed between the take-out pipe 60B and the tank 2B.

The number and arrangement of take-out pipes and the number and arrangement of joints are not limited to the above-described configuration.

In each of the inventions, the take-out pipe (60A) on the internal metal side (tank 2A side) does not have to be included.

The following describes modification examples in common between each of the inventions.

The basic insulation is not limited to the insulator, and insulation paper and the like may be used. Dipping may be performed on electronic parts.

The insulating bush is not limited to the one made of resin, and the one made of ceramic and the like may be employed. An insulating tube can be employed.

The number of tanks is not limited to two, and three or more tanks may be connected to one another in series. In this case, it is only necessary to electrically insulate between the tank positioned on the most downstream of the compressed air and the tank on its upstream side. Alternately, it is only necessary to electrically insulate between the tank positioned on the most downstream and the discharge port.

The upper housing may be divided into right and left parts without being divided into the front and rear parts. The upper housing may be formed in three or more division without limiting to two divisions. The upper housing may be an integral upper housing without being divided.

The lower housing may be formed by making the side plate high or the side plate may be omitted. A divided structure can be employed for the lower housing.

The motor is not limited to the outer rotor type and an inner rotor type is permissible. The motor does not have to be brushless and may be brushed.

The electronic parts, such as the pressure sensor, do not have to be disposed to the tank. In this case, as long as a resin-made base insulates between the main unit on the upper side and all the tanks on the lower side and an insulating bush and the like insulates a pipe linking the main unit and the tank on the most upstream, all the tanks can be external metals. in the application: 

1. An air compressor comprising: a motor provided with a basic insulation; a first air compressing unit and a second air compressing unit that are driven by the motor; at least two tanks that are connected to the first air compressing unit and the second air compressing unit, store air compressed by the first air compressing unit and the second air compressing unit, and are connected to one another in series; and a discharge port disposed to a tank positioned on a most downstream of supplied compressed air, the discharge port discharging the compressed air, wherein the motor, the first air compressing unit and the second air compressing unit, and a tank on an upstream side with respect to the tank positioned on the most downstream are electrically insulated from the tank positioned on the most downstream and the discharge port.
 2. An air compressor comprising: a motor provided with a basic insulation; a first air compressing unit and a second air compressing unit that are driven by the motor; at least two tanks that are connected to the first air compressing unit and the second air compressing unit, store air compressed by the first air compressing unit and the second air compressing unit, and are connected to one another in series; and a discharge port disposed to a tank positioned on a most downstream of supplied compressed air, the discharge port discharging the compressed air, wherein the motor, the first air compressing unit and the second air compressing unit, and all the tanks are electrically insulated from the discharge port.
 3. The air compressor according to claim 1, wherein the electrical insulation is performed by interposing a resin-made tubular body in a connecting pipe connecting the tank on the upstream side to the tank positioned on the most downstream, and by supporting the first air compressing unit and the second air compressing unit on the tank positioned on the most downstream via a resin member.
 4. The air compressor according to claim 3, wherein an insulating bush is further interposed between the tank positioned on the most downstream and the discharge port.
 5. The air compressor according to claim 2, wherein the electrical insulation is performed by interposing an insulating bush between the tank positioned on the most downstream and the discharge port.
 6. The air compressor according to claim 1, wherein at least the motor, the first air compressing unit and the second air compressing unit, and the tank on the upstream side are covered with a resin-made outer housing.
 7. The air compressor according to claim 2, wherein the motor, the first air compressing unit and the second air compressing unit, and all the tanks are covered with a resin-made outer housing.
 8. The air compressor according to claim 6, wherein the outer housing includes a lower housing on which the tanks are placed and an upper housing assembled to the lower housing from above the lower housing.
 9. The air compressor according to claim 8, wherein the lower housing and the upper housing are assembled with a screw, and an exposed portion of the screw in the outer housing is covered with a resin-made cover.
 10. The air compressor according to claim 9, wherein assembling of the lower housing and the upper housing is performed by screwing each of the screw passing through the lower housing and the screw passing through the upper housing into a metal fitting positioned in the outer housing.
 11. The air compressor according to claim 10, wherein the metal fitting is also covered with the cover.
 12. The air compressor according to claim 10, wherein positioning of the metal fitting is performed by inserting the metal fitting into a framing portion disposed in the lower housing and having an opened upper surface.
 13. The air compressor according to claim 12, wherein the lower housing includes a bottom plate and a side plate formed to rise around an outer periphery of the bottom plate, and the framing portion is formed on an inner side of the side plate.
 14. The air compressor according to claim 13, wherein the metal fitting includes a lower plate formed along a bottom surface in the framing portion and a vertical plate formed along the side plate such that the metal fitting has an L-shape, and the screw passing through the lower housing and the screw passing through the upper housing are screwed into the lower plate and the vertical plate, respectively.
 15. The air compressor according to claim 12, wherein the cover is fitted to the framing portion from above the metal fitting.
 16. The air compressor according to claim 9, wherein assembling of the lower housing and the upper housing with the screws is performed at a plurality of positions.
 17. The air compressor according to claim 8, wherein the upper housing is formed by assembling a plurality of divided housings.
 18. The air compressor according to claim 8, wherein the discharge port is exposed to an outside via a through hole provided in the outer housing.
 19. The air compressor according to claim 6, wherein a carry handlebar is disposed in the outer housing.
 20. The air compressor according to claim 6, wherein a pressure reducing valve and an operating member with which a pressure of the pressure reducing valve is adjustable are disposed between a second tank and the discharge port, and the operating member is exposed to an outside via a through hole provided in the outer housing.
 21. The air compressor according to claim 1, wherein the tank positioned on the most downstream is exposed. 